Jan 22, 2013

Some useful Underscore methods

I like jQuery and I use it in all my projects. Lately I've been looking into Design Patterns and Backbone framework. Backbone has a dependency on Underscore and more often than not, people use Underscore as a client-side templating engine when using Backbone. I was looking at the Underscore documentation and came across a bunch of useful methods.

where:

The where method looks into the array of objects and returns only those objects that contain the specified key value pairs:

This utility function would just shuffle the values in the list and every time you run this method it would return you a different shuffled list

_.shuffle([1,2,3,4,5,6,7,8]);
[3, 4, 8, 7, 6, 1, 2, 5]

memoize

Memoize allows you to cache the result of a function call. Say there is a function that returns the factorial of a number. If the function is called multiple times with the same value then memoize will return the cached result instead of calling the function.

Now on calling factorial(150) multiple times, the function is invoked only once and fetched from the cached in subsequent calls. When you look at the function definition it makes it clear that the data is returned from the cache and not by computing the result: